The invention relates to the use of radiant energy for the selective and controlled removal of ablatable material from a substrate without removing or damaging the substrate, and more specifically to an improved method and apparatus for smoothing or shaping a surface to preselected limits.
Many industrial procedures require the removal of a material or materials from a substrate or from adjacent materials in order to achieve a smooth surface. The wide variety of techniques used to perform this task include mechanical grinding, scraping, and blasting with sand or other abrasives. All of these methods have the disadvantages of being labor intensive and imprecise.
In U.S. Pat. No. 4,588,885, there is disclosed an automatic laser paint removal system for removing paint and other coatings from metallic or other substrates through an electronic control process. The control is accomplished by illuminating the area of the paint and the like which is to be stripped and subjecting the light reflected therefrom to spatial spectral dispersion. The spatial spectral dispersion is sensed and an electronic signal representative thereof is generated. The generated electronic signal is compared to a pre-recorded electronic signal representative of the spatial spectral dispersion of the paint or other coating(s) which are to be removed. This comparison is made before each pulse of high intensity radiant energy, and the pulse is applied only upon such comparison resulting in a substantial match.
The paint removal system described has some relation to the present invention, in that a surface condition is monitored and a decision is made whether to fire a scanning laser beam at each small unit of area covered, based on information just obtained by the monitoring for that unit of area.
The sensor system disclosed in U.S. Pat. No. 4,588,885 provides information for control of the firing of the laser only via the material at the surface of the area being stripped. The patented system does not provide or utilize a contour sensing subsystem and it is unable to accomplish the objective of the present invention, i.e. to achieve a desired contour.